Posted
by
Soulskill
on Friday June 10, 2011 @03:23PM
from the who-needs-a-jetpack dept.

Zothecula writes "Adventurous motorcyclists might be familiar with the thrill of getting airborne at the top of a rise, but the Hoverbike is set to take catching some air to a whole new level. With a 1170 cc 4-stroke engine delivering 80 kW driving two ducted propellers, the inventor of the Hoverbike, Chris Malloy, says with its high thrust to weight ratio, the Hoverbike should be able to reach an estimated height of more than 10,000 feet and reach an indicated airspeed of 150 knots (278 km/h or 173 mph). At the moment these are only theoretical figures as the Hoverbike hasn't been put through its paces yet, but Malloy has constructed a prototype Hoverbike and plans to conduct real world flight tests in a couple of months."

I'm not sure either - the center of gravity looks a little high, but the same is true of a Segway - or a bicycle, for that matter - gyro-controlled adjustments of the thrust vectoring might be the answer, or this thing might have similar intrinsic stability to a bike, allowing manual thrust vector control plus rider weight shifting to control roll at speed. The stability in hover would still be a potential problem, even so. With a pitch-controlled prop capable of reversing airflow, together with the right k

I was thinking "surely, they don't think just having vanes under the ducts will be enough to stabilise it?", but then I looked more closely at their photos. There aren't any. It has absolutely no roll control of any sort. I suppose you have some limited ability to balance using your body weight, but this is a kin to trying to balance a stationary unicycle.

My first impression was no roll control vanes, but a closer, calmer look revealed to me surfaces that might be for roll control. Nonetheless, this does look like a twitchy design. I'd want to see some very convincing numbers for recovery from high roll angles while hovering.

No that means that when the engine stops you plummet like a stone to earth. Unlike most helicopters which if they are unpowered and falling, the propellers will spin and provide some possibility of you not dying when you hit the ground. From wikipedia:

In helicopters and autogyros, autorotation refers to generation of lift by the main rotor when it is not being driven by an engine. Should an engine fail, a helicopter may be able to use autorotation lift to slow its descent and land in a controlled manner.

I'm pretty sure the landing gear is designed to crumple on impact. My buddy's dad was the plant manager at a helicopter manufacturer in Mexico and had lots of auto rotation stories where the pilot and passengers walked away from the "landing".

- Very safe. The hoverbike was designed with safety as the over-riding factor in all design. If you have ever flown and pre-flight checked a helicopter you will appreciate the simplicity of this design. With so many parts on a helicopter - and a large number of single parts that could alone cause catastrophic disaster if they should fail - it is just a matter of time. The hoverbike has as many components as possible with triple redundancy which requires at least 2 other components to fail before you migh

TFA says two parachutes on the "airfarme" (sic -- I would presume the mean "airframe") and an optional parachute for the pilot. So you would have the "option" of removing yourself from the vehicle, but theoretically shouldn't need to. If you have an engine failure as well as a failure in two ballistic recovery chutes AND both the main and reserve chute that you are wearing, you are having a Seriously Bad Day.

Not a problem. Add a rocket-powered ejection seat. Oh, wait, not in an airframe with an unadorned saddle and a dry weight of 240 pounds. A modern zero-zero egress system probably weighs close to that by itself.

Except during a really short timeframe during takeoff and landing, perhaps a combination of common sense and FAR 91.119 [gpoaccess.gov]? Yeah, I suppose 91.119 d might give you an out, but if you aren't worried about cruising around at an altitude that's high enough to kill you and low enough that you can't deploy a parachute, that's your call, I guess.

seriously slashdot, theres a difference between actual news and pure backyard bullshit.
anyone with even the most remote fucking grasp of physics and flight
should be comfortable debunking his claims as a complete lie.
most commercial helicopters stall out at anything greater than 8000ft; most of the ones flying around my city stick to around 600-800 ft ceilings..
The CH-47 Chinook twin rotor helicopter is used by the USAF to rescue climbers on Mount Denali (McKinley) in AK. It can reach an altitude in excess of 19000 to land at an elevation of around 18000.The biggest problem at that point is restarting the engines, so a special storage device directs pure oxygen into the engine inlet to restart.

the highest altitude helicopter currently in existence is the AS350. A pilot named Didier Delsalle of France landed it on the summit of Mount Everest (8,850 meters) in 2005...and the record is entirely speculative/disputed.

finally, A blackhawk military helicopter with a 1700 horsepower engine still only goes ~190 kias.

To build on this thought, it's 110kg dry, 20 liters of fuel ~20kg, and me, ~70kg, which is a nice round 200kg. This thing has 295kg of thrust, that's half a g acceleration after overcoming gravity. That's insane!.., that's 0-60 in 5.5 seconds! That's 0-1000ft in 11 seconds. At 10,000 ft there is only 70% air pressure, and 70% of 295 is close to 200 kg, making it the estimated ceiling.

You used 0 physics to rebuke his claim. You only supported your argument with non-analogous airframes.

I don't know if getting to 10K feet is possible with this thing, and I suspect it isn't--it wouldn't be matter of just air density, but also the rider would need protection, like air and temperature controls. Also the horizontal wind speeds would be a whole different factor, and it's not clear that he's taken those into account.

But shit, if it can fly stably at 30 feet at 50 mph that would be good enough for me. I could get off the roads, and therefore avoid traffic and use line of sight to travel.

Careful! Maybe he's got a concealed carry permit and one physic in a shoulder holster and another strapped to his leg. The leg one is for close quarters rebutting/rebuking or for after the one in the shoulder holster has been handed over.

Umm, 10,000 ft is not really that high. I regularly hike up mountains above that with a t-shirt on and no extra oxygen, I only really have a problem with breathing at above 12,000 ft and that's at a brisk walk, not flying around on an awesome machine. So as long as he's not straining himself, even coming from sea level you won't run into problems with HACE or HAPE (http://en.wikipedia.org/wiki/High_altitude_cerebral_edema http://en.wikipedia.org/wiki/High_altitude_pulmonary_edema [wikipedia.org]) unless you're up there f

The boiling temperature of water @ 10,000 ft is only about 10 degrees lower than at sea level. For aeronautics purposes anything under 10k ft is mostly the same density. That might be different for a heavily laden cargo plane, but 10k ft is a pretty safe design envelope.

anyone with even the most remote fucking grasp of physics and flight should be comfortable debunking his claims as a complete lie.

From your comments below, I take it you aren't one of those people. Here goes:

most commercial helicopters stall out at anything greater than 8000ft; most of the ones flying around my city stick to around 600-800 ft ceilings..

Those two statements have little, if anything, to do with each other. Helicopters generally stick to low (sub 1,000 ft) altitudes for a couple of reasons -- namely, there's usually little reason to fly higher since it takes more fuel to climb and the jobs for which they are often used tend to require low altitude flight -- not because they are incapable of flying higher. Also, the ceiling for a helicopter is dependent upon its forward velocity through the air. The faster the helicopter flies -- to a point -- the more lift the rotor blades create, and therefore, the higher it can fly, so be careful not to confuse the hovering ceiling with the service ceiling in cruise flight. They are not the same thing.

The CH-47 Chinook twin rotor helicopter is used by the USAF to rescue climbers on Mount Denali (McKinley) in AK.

Uhhh...no, it's not. The Air National Guard based at Kulis in Anchorage flies Sikorsky Pavehawks (militarized S-70s) and the Army at Ft. Rich flies the Blackhawk -- basically the same airframe as the Pavehawk, but outfitted differently. In Talkeetna, AK (where most climbers fly out of to reach Denali), there is a highly modified helicopter nicknamed the "Denali Lama". IIRC, it's an Aerospatiale -- but it's definitely NOT a CH-47. In fact, I'm not aware of anyone regularly flying a CH-47 in Alaska; at least I don't see them in Anchorage very often.

the highest altitude helicopter currently in existence is the AS350. A pilot named Didier Delsalle of France landed it on the summit of Mount
Everest (8,850 meters) in 2005...and the record is entirely speculative/disputed.

finally, A blackhawk military helicopter with a 1700 horsepower engine still only goes ~190 kias.

And your point is? A Cessna 206 does 140 knots [cbp.gov] (the article doesn't say on what engine, but 206s typically have either a Continental O-470 at ~235 h.p. or a Lycoming O-520 at ~300 h.p.), but the amateur-built AR-5 will do [ar-5.com] 180 kts [google.com] on 65 h.p. Let's see...the AR-5 has 1/5 the power and roughly 1.5 times the speed. Clearly you can't correlate h.p. to max speed on different airframes. In fact, there's a lot that determines how fast a given amount of power will propel an aircraft, for example, the drag from the rotor disk and how much of that engine power goes into lifting the aircraft. Your 1700 h.p. Blackhawk has a max take-off weight of 23,500 pounds [wikipedia.org], giving a power to weight ratio of 0.07 hp/pound. Since the designer of the hover bike is shooting to classify this aircraft as an ultralight in the U.S., that means he's limited to an empty weight of 254 pounds. [usua.org]

There's an additional factor that makes the blackhawk comparison invalid. The hoverbike's fans sweep a pretty small area. The smaller the area, the higher the speed through the fan needed to produce the same thrust. That higher speed means energy wasted accelerating air. I don't know the math, so what we need here is some aero engineer to provide a good estimate and some rough guidelines. Any volunteers?

Except this is the exact reason it's stable, and the exact reason helicopters are unstable, because the mass sits below the gyros. See Hiller flying platform [youtube.com], just leaning made it move. The next model the military made had larger fan blades and was too stable, even if the pilot leaned as much as he good he couldn't get it to tilt and therefore move.

A Segway is inherently unstable. It's just the inverted pendulum [wikipedia.org] control problem. In this case, there will be an onboard computer doing the stabilization. That's well within our capabilities.

Airplanes have to ability to glide to an extent, helicopters can auto-rotate. I seriously doubt that the rotors on this are big enough to auto-rotate, or that the designer made the calculations necessarily in order to design something that can auto-rotate.

You could use a parachute but parachutes take time to deploy and slow your decent so while effective at higher altitudes, at lower altitudes, like say the altitude at which you would be herding cattle, an engine failure would leave you heading towards the ground without enough time to deploy the chute.

I'd fly this is there were 2 engines such that one engine could power both fans, and 1 engine had enough power to at least hover and make a safe decent. Even then, I'd still probably bring a parachute.

Helicopters have a similar problem. For given combinations of altitude and forward velocity, they can't auto-rotate. Consequently, helicopter pilots attempt to minimize the amount of time they spend transitioning from lift-off to forward flight in order to minimize the amount of time they spend in a flight condition where an engine failure is catastrophic. With regards to the hoverbike...get your butt UP as fast as you can.

How about adding a backup parachute system to the hoverbike itself? That is, it quickly ejects a parachute for the bike and rider when power is lost in the air. Since it's much lighter than a helicopter, it might work. I dunno.

that deep pitch is the cup.. and while it allows for more thrust at lower RPM it limits your max RPM which limits your max throughput. it can also cause disturbance behind the blade which can cause cavitation at higher RPM

For hover applications where the air doesn't need to be moved fast, maximum rotor diameter is always the best, because it lets you move the blades relatively slowly, avoiding parasitic drag (air friction) while still moving a lot of air. That's why helicopters have such big rotors. With this hoverbike, practical matters dictate that the prop diameter is very limited, meaning that in order to move enough air, you need to spin the blades really fast. In order to not waste all energy on air friction, the blade

Having previous experience in a helicopter or plane would be a great help. That said, this is a new way to fly and one would need to learn to ride the hoverbike in much the same manner as a helicopter or riding a motorcycle. If you live in the USA or your country has similar civil aviation regulations, then the hoverbike will be classed as a 'ultralite' which means you do not need a pilots license to fly the hoverbike.

From the summary of vehicle regulations for ultralight aircraft at http://www [ultralightflying.com]

I am pretty sure its stall speed is going to be 0 laterally, and that is less than 28mph, so he may still qualify. Unless of course that stall speed accounts for vertical motion, in which case his is going to be approximately terminal velocity.

Agreed. It wouldn't be hard to shave off capability until it fits the regulatory guidelines. Of course, since the regulatory guidelines aren't built around the idea of a direct-lift rotorcraft which has to expend engine power just to get off the ground, the Hoverbike's at a distinct disadvantage compared to current-technology ultralights. TBH, as you point out, if you shave off enough capability, you've probably eliminated any practicality.

My answer would be either NaN [codingforums.com] or null. 1) It has no wings, just the ducted fans, so the only airfoil that could stall would be the propellers. 2) If the power is off, the props aren't providing any appreciable lift (since it doesn't auto-rotate). 3) Therefore, the concept of "power-off stall speed" doesn't really apply.

If the power is off, you're making like a brick until/unless you deploy the ballistic recovery chute.

It seems like the Hoverbike seems to be a lame attempt to cash in on the success of the Martin Jetpack [martinjetpack.com].

To me, the Hoverbike looks like a deathtrap: the pilot is sitting above the lift propellers and with a centre of gravity higher than the centre of lift and no apparent method for lateral stabilization it will tip over the moment the pilot leans to far to one side. In their FAQ, they attempt to brush off the stability issue by talking about fixed-wing aircraft: aircraft that don't hover and that have a la

With a 1170 cc 4-stroke engine delivering 80 kW driving two ducted propellers, the inventor of the Hoverbike, Chris Malloy,
Wow, those are some impressive stats. He should be able to hover even WITHOUT the hoverbike.

Well...if it's like two of the three bikes I've owned, you switch to the reserve tank and hope the carburetor float bowl refills before you hit the ground. The third bike has a fuel gauge, which does wonders for preventing you from running out of gas.

1. Guy goes too fast on hoverbike
2. Kid runs after ball, runs in front of bike, then realizes the guy is riding at least 50 ft above him, then he gets his ball
3. Bike makes no attempts to stop since it is far above the boy on the street
4. Bike passes kid harmlessly remaining upright and under control
5. Kid looks at oncoming car in horror
6. Mel Gibson runs over kid and yells, "You Abo scum will not grow up to sleep with me wife!

Please explain by how pointing out the same has been said in the past about other vehicles that I am making "it sound like machines can still be built by amateurs and be safe". I neither implied nor inferred that anywhere, and was wondering how you came to that conclusion.

I've actually done a little experimenting with the gyroscopic effect of a bicycle wheel. It has to be spinning very fast or be artificially heavily weighted to be have forces large enough to help keep the bike upright. In actual practice, it doesn't help at all. If you don't correct with steering or balance changes, no amount of gyro force is going to keep a bike upright. Furthermore, the spinning wheel also opposes the turning of the handlebar which is the cyclist's primary tool for keeping a bike upright.